Comparison

Celsius vs Fahrenheit

Two everyday temperature scales — same physics, different zero points and step sizes.

	Celsius (°C)	Fahrenheit (°F)
Water freezes	0 °C	32 °F
Water boils	100 °C	212 °F
Body temperature	37 °C	98.6 °F
Step size	1 °C = 1.8 °F	1 °F = 0.56 °C
Used by	Almost every country	USA, Cayman Islands, Belize

Celsius (°C) pros

Aligns with the metric system
Easy 0 / 100 reference points
Used by all scientific literature

Fahrenheit (°F) pros

Finer step size for ambient weather
Familiar to US audiences
Maps weather to a 0–100 'feels like' scale

When to use which

Use Celsius (°C)

Use Celsius for science, cooking with metric recipes, and anywhere outside the US.

Use Fahrenheit (°F)

Use Fahrenheit when speaking to a US audience about weather or comfort.

Historical context

Daniel Gabriel Fahrenheit published his scale in 1724, fixing zero at the coldest temperature he could reliably reproduce with a brine mixture and setting human body temperature near 96. Anders Celsius followed in 1742 with a scale divided into a hundred steps between the freezing and boiling points of water — but the wrong way round, with 0 for boiling and 100 for freezing. It was inverted to the modern arrangement shortly after his death. The practical consequence of the two designs is that they disagree about both where zero sits and how large a degree is: there are 180 Fahrenheit degrees between the freezing and boiling points where Celsius has 100, which is where the 9/5 ratio comes from. Both scales are now defined in terms of the kelvin rather than water. Only the United States and a few small territories still use Fahrenheit for everyday weather; virtually all scientific work everywhere uses Celsius or kelvin.

Practical recommendation

Use Celsius unless you are writing for a United States audience about weather, cooking or body temperature, where Fahrenheit remains what people actually feel in. For anything scientific, medical or engineering, Celsius is the right default and kelvin is required wherever absolute temperature enters a calculation. If you are converting in your head, remember the two scales cross at −40, and that a change of 5 °C is a change of 9 °F — for differences you scale by 9/5 and never add the 32, because the offset cancels.